This invention relates to coating compositions and systems, and more particularly to aqueous or water-base coating compositions, and methods of making and using the same.
Coating untreated polyolefin-containing substrates, such as polypropylene substrates, is generally difficult because of poor adhesion of coatings to this type of substrate.
In an effort to solve this problem, polyolefinic and other similar plastic or synthetic substrates have been typically coated with coating systems employing an organic solvent base. While the use of organic solvents appears to assist, to some degree, the organic contents of the coatings often render the coating composition or system undesirable from a number of aspects. For example, most organic solvents are derived from petroleum products, and thus are generally expensive and in short supply. Further, unless suitable costly recovery or disposal procedures are used, organic solvents, such as the commonly used aromatic organic solvents, may create a potential pollution problem.
Other popularly employed coatings include chromium-containing coatings. And like petroleum-based systems, unless properly controlled costly recovery or treatment methods are also employed, chromium-containing coatings are also potentially undesirable from an environmental standpoint.
Aqueous-based primer coatings, additionally employing substantial levels of aromatic organic solvents, have been suggested in the art. For example, such compositions have been disclosed by manufacturers or distributors such as Eastman Chemical Corp. Likewise Emco Chemical Corporation has disclosed a primer for polypropylene that includes, as initial ingredients 25% by weight of a chlorinated polyolefin having a chlorine content of 30% (25% in xylene), 24.925% toluene, 0.025% sulfonated castor oil, 0.050% sodium lauryl sulfate, and 50.000% deionized water (as a final ingredient).
U.S. Pat. No. 4,954,573 (incorporated by reference) discloses a chlorinated polyolefin composition for use as a primer or coating or various types of substrates, such as polyolefins.
The use of chlorinated polyolefin materials as a primer for polyolefin substrates has also been proposed. For instance, U.S. Pat. No. 4,303,697 (incorporated by reference) discloses priming a polyolefinic substrate with a chlorinated polymeric material, such as chlorinated polypropylene, containing carboxylic acid anhydride groups, and exposing the primed substrate to ultraviolet radiation.
U.S. Pat. No. 4,070,421 (incorporated by reference) discloses chlorinated polyolefinic compositions useful as primers for adhesion improvement of decorative or protective coatings to polyolefins.
U.S. Pat. No. 3,579,485 (incorporated by reference) discloses chlorinated carboxyl group-containing poly-.alpha.-olefins, which form primer coatings for use on untreated poly-.alpha.-olefin substrates, and halve aromatic solvents as a preferred solvent.
The following United States patents, which are incorporated by reference herein, relate more generally to coating compositions for substrates, including coating compositions for polyolefin substrates: U.S. Pat. Nos. 4,710,408; 4,567,106; 4,417,022; 4,343,925; 4,317,894; 4,314,918; 4,263,411; 4,246,319; 4,214,039; 4,144,363; 4,046,587; 4,028,329; 3,849,148; 3,317,330; 3,218,189; and 2,998,324.
It is therefore an object of the present invention to provide an aqueous-based coating composition, with a reduced level of, or substantially free of, volatile organic components ("VOC's") or solvents (such as aromatic organic solvents) for coating substrates such as polyolefin-containing substrates.
The compositions and methods of the present invention preferably employ: (a) a resin; (b) an ethylene glycol; (c) a surfactant; (d) an aliphatic amine; and (e) water. In another embodiment the compositions and method further employ a thickening agent, a filler, or both.